The present invention relates to an image reading apparatus.
An image reading apparatus (see JP-A-2001-133906) mounted with a contact image sensor module has heretofore been known. Since an optical system of the contact image sensor module has a short optical path, it is easy to reduce the size of the image reading apparatus.
However, since the contact image sensor module has a shallow depth field, the image reading apparatus cannot clearly read a document placed at a position away from a platen surface of a document platen. For example, an image reading apparatus described in JP-A-2001-133906 cannot clearly read a 35 mm film or the like held by a holder.
Image reading apparatuses described in JP-A-2003-37712 and JP-A-2003-37713, each including a plurality of optical systems, can clearly read a reflective document and a transmissive document by changing an optical path in response to the document. However, the image reading apparatuses described in JP-A-2003-37712 and JP-A-2003-37713, the optical systems of which have a complex configuration and a long optical path, have the problem in which they are high in manufacturing cost and unfit for a reduction in size.
A first linear image sensor and a second linear image sensor are disposed to provide a configuration such that an optical image of a document placed on the platen surface of the document platen is focused onto the first linear image sensor, and such that an optical image of a document placed at a position away from the platen surface of the document platen is focused onto the second linear image sensor. Such a configuration makes it possible to clearly read the document placed on the platen surface of the document platen and the document placed at a position away from the platen surface of the document platen.
When provided with the two linear image sensors parallel to each other, the contact image sensor module is increased in size in a sub scanning direction. As the contact image sensor module is increased in size in the sub scanning direction, when a support supports an end portion of the document platen in the sub scanning direction, it follows that the support must be displaced in the sub scanning direction so as not to hinder when the contact image sensor module has been transported to an end. However, when the support is displaced in the sub scanning direction, the document platen must be extended in the sub scanning direction by an amount equivalent to the displacement, which raises the problem of an increase in size of the document platen.